I didn't realize I was going to have the cover story of the latest New Scientist with this in-depth article I did about the climate-tornado relationship. Essentially, the bottom line is this--it's even more complicated than the climate-hurricane relationship. And so for all those politicians, environmentalists, and bloggers out there who want to use tornadoes (and especially this extremely active U.S. tornado year) as an excuse to talk about global warming...well, the science provides a slender foundation for them indeed.
You can't read the full New Scientist article online, but let me lay out the core scientific reason that we can't say much about tornadoes right now. The data are way, way too bad to detect reliable trends, and as for the theory/modeling...well, that's not far enough along either. Scientists are just starting to be able to use climate models to predict environmental changes that could favor severe thunderstorms (which generate tornadoes). But because not all severe thunderstorms are tornadic, and because tornadoes are far too tiny to capture in models, and because the reasons for their genesis are incompletely understood, this line of inquiry can't really go any farther right now--at least not yet.
Here's the relevant excerpt from the piece. Unfortunately, you really need more context than this brief slice, but at least the core scientific points are there:
What about tornadoes? Del Genio says it is "plausible" that their numbers or other
attributes could change as well, but adds that his study couldn't directly predict this. "Telling the difference between severe storms in general, and the particular ones that produce tornadoes, that's the most difficult thing to do," he adds.A similar conclusion emerged from the second study, done by Jeff Trapp of Purdue University, Indiana in collaboration with Brooks and others. They also found that global warming should increase CAPE but decrease overall wind shear. Higher CAPE more than makes up for lower wind shear, though: they predict that by the end of the century there will be an increase in the number of days in the US when conditions favour severe thunderstorms.
For Trapp, as for Del Genio, there is still not enough information to make a firm prediction. "What we did is sort of the low hanging fruit," Trapp says. "Trying to separate out this frequency of severe thunderstorms from the frequency of tornadoes explicitly is much higher in the tree."
So, environmentalists be warned...
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That cover reminded me of something, and it took a while to recall it, but I remember old comic books invariably mentioning the death of main characters on the cover and (almost) never delivering on the promise on the inside. Are the current editors of major media former comic-book readers, or maybe former comic-book editors? Covers and headlines are such bull. The only good news is that sometimes the journalist has a clue what the scientists interviewed actually said. I consider you one of the few, so thank you.
If a tornado fells a tree in the forest, and nobody is there to hear it, does it make a sound?
Don't know if your article covers this, hope it does: Tornado counts before Doppler weather radar can't be compared directly to counts after Doppler radar. I guess I sound like those who warn we can't be certain of hurricane frequency because we've only been able to count them reliably since weather satellites. The quandary is more pronounced with tornadoes because they are so localized.
Maybe another approach to the climate connection is, is their observed incidence moving poleward? We just had a fatal tornado in New Hampshire, newspapers said that was unusual and I can't recall that happening before. Tornadoes a few miles more south in Mass. are not that unusual.
The connection is tenuous, as you point out, but there was an interesting post in a weather forum recently by a professional meteorologist which indicated that there has been a marked increase in the number of hail reports in the Northeast, upstate NY in particular.
"And so for all those politicians, environmentalists, and bloggers out there who want to use tornadoes (and especially this extremely active U.S. tornado year) as an excuse to talk about global warming...well, the science provides a slender foundation for them indeed."
And yet when Randy Olson did precisely that in "Sizzle" using Katrina, you saw nothing whatsoever wrong with that. Your frame is slipping, Chris.
But congratulations on the New Scientist cover and article. That's quite an achievement.
BTW, this is something Tamino has examined a little.
http://tamino.wordpress.com/2008/05/13/attack-of-the-50-foot-tornado/